This invention relates to liquid flow control valves, and more particularly to water flow control valves used in farmland irrigation.
In the irrigation of crops which are planted in rows, it is common to introduce water at the high end of a field in order that the water may flow by gravity down the furrows to the opposite end of the field. In one method of such irrigation, commonly called continuous irrigation, water is continuously introduced at the high end of the field until the water has reached and had sufficient time to soak the low end of the field. This method of irrigation is not efficient because a considerable amount of water is wasted in run-off at the low end of the field and in soaking into the ground deeper than the plant root zone at the high end of the field.
An improved method of furrow irrigation, called "surge irrigation" applies water at the high end of the field in a series of timed increments, allowing the soil to dry between the alternate wettings. When the soil is thus wetted and allowed to dry, a thin seal forms on the soil surface reducing the soil's permeability. The alternate wetting and drying of the higher end of the field and the formation of the thin seal speeds the advance of water down the furrow during subsequent wettings and minimizes unnecessary over-soaking of the high end of the field.
In the practice of surge irrigation, farmers have found it most efficient to use an automatic flow control valve to direct the flow of water to either of two distribution pipes on the high end of the field, each of which applies water to a different set of furrows. Such a valve applies the water to each such distribution pipe in sequence, so that while one set of furrows is being wetted, the other set is drying. The valve commonly used is a standard butterfly valve operated by an attached electric motor. Because the valves and distribution pipes are usually located beyond the reach of electric utility lines, and because they must be frequently moved from place to place in the field, the valve motors are typically powered by automotive storage batteries. Use of such valves has caused problems, principally arising out of the fact that the battery is heavy and must be frequently recharged due to the large power consumption of the motor. Furthermore, the design of butterfly valves causes a flow restriction which reduces the flow rate through such conventional valves. As a result, sand which is entrained in irrigation water, settles to the bottom of the valve and hinders proper valve function.